I receive many emails from users and I enjoy all of them. Those emails (and messages in this blog, and reviews) are my primary source for feeling what is good and what is wrong with ShopList. Since ShopList was released I have come with two main sources of confusion that need special attention and I'll describe them and the solutions I came up with.
Subtracting from the total
Why does uncheking and item (moving from Have to Need) does not subtract from my total in a list with prices? Well, there is no real good answer. The main issue is when should is subtract? Sometimes I want to get something I bought and remove it from my cart just because I changed my mind: in this case it should subtract. But if I'm adding an item to my Need list because I just remembered I need it, it should not. This two cases need to be distinguished to be able to subtract correctly.
My plan for a solution goes as follows. Items in the Have section that are part sum for the current total will have a light blue background color. Items that are not part of the total will just be the regular white (see picture).
When an white item is uncheked it will not subtract from the total; when a blue item is unchecked it will subtract from the total. Doing the swipe to delete the total will also clear make all the blue items white. In the example the $7.00 are the total from the Bananas and the Soy Milk (both the blue). Uncheking Bananas would bring the total to $2, while uncheking Cereal would remain the total unchanged.
I think this is an elegant and clear solution to the problem. It requires understanding of the white/blue semantics, but I think it will do fine.
Quantity times Price
Why when I check (move from Need to Have) 3 bananas with a price of $1 the total add $1? Shouldn't it add $3?. Well, again no clear answer. Right now prices and quantities are somewhat independent. So the price you set for an item is the total price for that item, regardless of the quantity. The reason behind this is that it is more flexible, what if I decided to get 4 bananas? Well, if the quantity is set to 3 and I want to add $4 to the total I'm in trouble.
It is confusing and that is why I'm planning the following change. When setting the price for a item, the key pad will allow for the quantity to be updated too (see image).
Besides the price field there will be a multiplier, set to 1 if no quantity is set of to the quantity if it is set. This will allow for an easy input of either the total or the unit price of your purchase. Again I think the solution makes this issue less confusing with out complicating the interface that much.
This changes are planned to come with ShopList 1.2 (1.1 is coming out any day now, but mainly fixes bugs).